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Saturday, November 12, 2011

Ten years ago Passarino et al. released a paper focusing on the origins and spread of R1a1a (back then known as Eu19). They did this by studying the frequency and diversity of the 49a,f/TaqI haplotype 11, which appeared to be linked to R1a1a. The conclusion was that R1a1a most likely originated in present day Ukraine, and expanded from there into Europe and Asia.

However, a couple years later, STR diversity became the method of choice for studying Y-DNA haplogroup origins and expansions, and the information provided by 49a,f/TaqI Ht11 was basically ignored.

Despite lots of quirky results since then, like placing the ancestors of some modern populations far in Northern Europe when it was still covered with massive ice sheets, no one in academia attempted to challenge the new methodology until this year (see here). However, in the meantime, it was "discovered" that India harbored the greatest diversity in R1a1a STRs, and was thus hailed as the place of origin of this widespread paternal marker.

It seems we've now come full circle, because latest work on the SNP structure within R1a1a shows that India has very low R1a1a diversity. For instance, all Indians tested to date for newly discovered R1a1a SNPs, mostly as part of various private Y-DNA projects, have come back positive for the Z93 mutation. This marker is not upstream to any European R1a1a subclades. In fact, most Eastern Europeans tested to date have come back ancestral for Z93. This information gels very well with ancient DNA results, which show a movement of light-pigmented European-like groups deep into Asia during the early metal ages from somewhere in West Eurasia (see here).

The news just in, courtesy of the R1a and Subclades Y-DNA Project, is that the Z283 SNP ties together the three major European R1a1a subclades. These are R1a1a1-Z284, largely found in Scandinavia, R1a1a1-M458, characteristic of Western Slavic and Eastern German populations, and R1a1a1-Z280, of Central and Eastern Europe. The primary distribution of Z283 shows an uncanny resemblance to that of the former Corded Ware cultural horizon of Northern Europe. Below is a map of the Corded Ware zone from Haak et al. 2008, which describes the discovery of R1a1a in the ancient remains from a Corded Ware burial in what is now Eastern Germany.